TYPO3 Core

Forgot to mention that this happens in Opera 9.26.

This happens also when user installs extensions. See second screenshot (em-in-opera.png)

I think that's all because the docheaders, Opera has problems with position absolute
Web>page: big margins at the bottom
Web>list: big margin on the top, big margins at the bottom
filelist: big margin at the top
etc.

I don't see the big margins, sorry. It looks okay for me in Opera. The EM display errors are also much worse than anything in the file list or the web modules, so it can't (just) be the docheaders.
I may can take a look at it later.

i attached a screen of the margins (Opera 9.26)

but you're right that EM is worse because it's unusable that way.

I found the problem:
EM Module used nested forms, which is wrong and invalid markup.

Attached patch corrects this.

tested and works.

i attached a more complete patch with corrections in submodules of EM too.

Once again i digged through whole code (over 5000 lines and many forms)

I corrected all forms now, please test again and check all functions.

I guess this bug is related to that one: http://bugs.typo3.org/view.php?id=7771

I found one new issue and fixed bug from #18383 too in
7682_em_wrong_markup4.diff

and no. 5 which solves a new issue.

attached try_again.png. The submit button there doesn't work either. You may have already fixed that, if so, ignore it.

Applied your patch 5 and it does indeed fix that, so awesome, thanks!